StraightLineCylinderCrossing Class Reference

#include <StraightLineCylinderCrossing.h>

Public Member Functions
std::pair< bool, double >	pathLength (const Cylinder &cyl) const
LocalPoint	position (const double s) const
	StraightLineCylinderCrossing (const LocalPoint &startingPos, const LocalVector &startingDir, const PropagationDirection propDir=alongMomentum, double tolerance=0)

Private Types
typedef LocalVector	DirectionType
typedef Basic2DVector< float >	DirectionType2D
typedef LocalPoint	PositionType
typedef Basic2DVector< float >	PositionType2D

Private Member Functions
std::pair< bool, double >	chooseSolution (const double s1, const double s2) const
	Chooses the right solution w.r.t. the propagation direction. More...

Private Attributes
const DirectionType	theP0
const PropagationDirection	thePropDir
double	theTolerance
const PositionType	theX0

Detailed Description

Calculates the intersection of a straight line with a barrel cylinder.

Definition at line 17 of file StraightLineCylinderCrossing.h.

Member Typedef Documentation

DirectionType

typedef LocalVector StraightLineCylinderCrossing::DirectionType

private

Definition at line 47 of file StraightLineCylinderCrossing.h.

DirectionType2D

typedef Basic2DVector<float> StraightLineCylinderCrossing::DirectionType2D

private

Definition at line 49 of file StraightLineCylinderCrossing.h.

PositionType

typedef LocalPoint StraightLineCylinderCrossing::PositionType

private

Definition at line 46 of file StraightLineCylinderCrossing.h.

PositionType2D

typedef Basic2DVector<float> StraightLineCylinderCrossing::PositionType2D

private

Definition at line 48 of file StraightLineCylinderCrossing.h.

Constructor & Destructor Documentation

StraightLineCylinderCrossing()

StraightLineCylinderCrossing::StraightLineCylinderCrossing	(	const LocalPoint &	startingPos,
		const LocalVector &	startingDir,
		const PropagationDirection	propDir = alongMomentum,
		double	tolerance = 0
	)

Constructor in local frame

Definition at line 10 of file StraightLineCylinderCrossing.cc.

    : theX0(startingPos), theP0(startingDir.unit()), thePropDir(propDir), theTolerance(tolerance) {}

Member Function Documentation

chooseSolution()

std::pair< bool, double > StraightLineCylinderCrossing::chooseSolution ( const double  s1, const double  s2  ) const

private

Chooses the right solution w.r.t. the propagation direction.

Definition at line 49 of file StraightLineCylinderCrossing.cc.

References alongMomentum, anyDirection, SiStripPI::min, thePropDir, and theTolerance.

Referenced by pathLength().

                                                                                                         {
  //
  // follows the logic implemented in HelixBarrelCylinderCrossing
  //
  if (thePropDir == anyDirection) {
    return std::pair<bool, double>(true, (fabs(s1) < fabs(s2) ? s1 : s2));
  } else {
    int propSign = thePropDir == alongMomentum ? 1 : -1;
    if (s1 * s2 < 0) {
      // if different signs return the positive one
      return std::pair<bool, double>(true, ((s1 * propSign > 0) ? s1 : s2));
    } else if (s1 * propSign > 0) {
      // if both positive, return the shortest
      return std::pair<bool, double>(true, (fabs(s1) < fabs(s2) ? s1 : s2));
    } else {
      // if both negative, check if the smaller (abs value) is smaller then tolerance
      double shorter = std::min(fabs(s1), fabs(s2));
      if (shorter < theTolerance)
        return std::pair<bool, double>(true, 0);
      else
        return std::pair<bool, double>(false, 0.);
    }
  }
}

pathLength()

std::pair< bool, double > StraightLineCylinderCrossing::pathLength

(

const Cylinder &

cyl

)

const

Propagation status (true if valid) and (signed) path length along the line from the starting point to the cylinder.

Definition at line 16 of file StraightLineCylinderCrossing.cc.

References chooseSolution(), dttmaxenums::R, Cylinder::radius(), theP0, theX0, PV3DBase< T, PVType, FrameType >::x(), and PV3DBase< T, PVType, FrameType >::y().

Referenced by HelixBarrelCylinderCrossing::HelixBarrelCylinderCrossing(), and RKPropagatorInS::propagateParametersOnCylinder().

                                                                                             {
  //
  // radius of cylinder and transversal position relative to axis
  //
  double R(cylinder.radius());
  PositionType2D xt2d(theX0.x(), theX0.y());
  //
  // transverse direction
  //
  DirectionType2D pt2d(theP0.x(), theP0.y());
  //
  // solution of quadratic equation for s - assume |theP0|=1
  //
  RealQuadEquation eq(pt2d.mag2(), 2. * xt2d.dot(pt2d), xt2d.mag2() - R * R);
  if (!eq.hasSolution) {
    /*
    double A=   pt2d.mag2(); 
    double B=   2.*xt2d.dot(pt2d);
    double C=   xt2d.mag2()-R*R;
    cout << "A= " << pt2d.mag2() 
     << " B= " << 2.*xt2d.dot(pt2d)
     << " C= " << xt2d.mag2()-R*R
     << " D= " << B*B - 4*A*C
     << endl;
    */
    return std::pair<bool, double>(false, 0.);
  }
  //
  // choice of solution and verification of direction
  //
  return chooseSolution(eq.first, eq.second);
}

position()

LocalPoint StraightLineCylinderCrossing::position ( const double  s ) const

inline

Returns the position along the line that corresponds to path length "s" from the starting point. If s is obtained from the pathLength method the position is the intersection point with the cylinder.

Definition at line 36 of file StraightLineCylinderCrossing.h.

References alignCSCRings::s, theP0, and theX0.

{ return LocalPoint(theX0 + s * theP0); }

Member Data Documentation

theP0

const DirectionType StraightLineCylinderCrossing::theP0

private

Definition at line 52 of file StraightLineCylinderCrossing.h.

Referenced by pathLength(), and position().

thePropDir

const PropagationDirection StraightLineCylinderCrossing::thePropDir

private

Definition at line 53 of file StraightLineCylinderCrossing.h.

Referenced by chooseSolution().

theTolerance

double StraightLineCylinderCrossing::theTolerance

private

Definition at line 54 of file StraightLineCylinderCrossing.h.

Referenced by chooseSolution().

theX0

const PositionType StraightLineCylinderCrossing::theX0

private

Definition at line 51 of file StraightLineCylinderCrossing.h.

Referenced by pathLength(), and position().